The present invention relates compressors, specifically compressors having crankshafts with eccentrics thereon.
A crankshaft, or drive shaft, operatively couples the motor and compression mechanism of a compressor assembly.
A problem with previous crankshafts was that they were unbalanced when used unless large counterweights were added to achieve a balanced state. An example of such a previous crankshaft may be seen in FIGS. 3a and 3b in which crankshaft 10 is shown as having a cylindrical eccentric portion 12 formed with the shaft. As seen in FIG. 3b, centerline 18 of eccentric 12 is offset from and parallel to centerline 20. In order to achieve a center of mass near the axial center of shaft 10, weight 14, nearly equal to the weight of eccentric 12, is placed at the opposite end of shaft 10 (upper end 15 as shown) and on the same radial side of the shaft as eccentric 12. Although this did place the center of gravity nearer the center of shaft 10 end for end, the addition of weight 14 nearly doubled the shaft""s eccentric weight. So, additional weight 16 was added to the radial side of crankshaft 10 opposite from eccentric 12. Weight 16 is nearly double that of eccentric 12, and balances all dynamic forces. Thus, the overall weight of crankshaft 10 was greatly increased, by approximately four times the weight of eccentric 12 alone, in order to balance crankshaft 10.
The additional weight can result in decreased efficiency of the compressor. As the compressor operates, the shaft must be rotated to operate the compression mechanism. With the additional weight, the inertia of the crankshaft increases causing the crankshaft to become more difficult to rotate and the load on the motor to increase. This increase in loading on the motor may lead to motor failure, resulting in downtime for the compressor and potentially expensive repairs.
Previous attempts at reducing the rotating inertia of a compressor have included drilling bores in a crank journal to reduce weight (U.S. Pat. No. 3,513,721), using perforated disks as part of a counter balance unit (U.S. Pat. No. 3,876,344), using variously shaped counterweights (U.S. Pat. Nos. 4,867,007 and 4,611,503), or using dual counterweights located on the eccentric (U.S. Pat. No. 5,033,945).
Not only is the weight itself a problem, but more space is required inside the compressor to accommodate the weights. For example, the weights added to the shaft may require that height be added to the compressor to accommodate the weights. Also, each additional weight adds to the expense of the compressor.
A compressor assembly which includes a crankshaft having a reduced weight for improved efficiency, reduction in housing space, and a less expensive compressor would be desirable.
The above-described shortcomings of previous compressors are overcome by providing a hermetic compressor assembly including a compressor housing, a compression mechanism disposed in the housing, a motor disposed in the housing, and a crankshaft operatively coupling the compression mechanism and the motor. The crankshaft has an axis of rotation and includes a cylindrical eccentric having a central axis located on one side of the axis of rotation and a counter eccentric lobe integrally formed with the crankshaft on the opposite side of the crankshaft from the eccentric and being axially adjacent the eccentric.
The present invention provides a hermetic compressor assembly including a compressor housing, a compression mechanism disposed in the housing, a motor disposed in the housing; and a crankshaft operatively coupling the compression mechanism and the motor and having an axis of rotation. The crankshaft includes a cylindrical eccentric and a counter eccentric lobe. The cylindrical eccentric has a central axis, defines a circular axial profile, and is located on one radial side of the axis of rotation. The counter eccentric lobe is integrally formed with the crankshaft on the opposite side of the crankshaft from the eccentric, is axially adjacent the eccentric, and is located within the circular axial profile.
In one embodiment of the present invention, the hermetic compressor is a rotary compressor assembly and the compression mechanism includes a cylinder block and bearing assembly in the housing. The cylinder block and bearing assembly define a cylindrical cavity and a roller piston is disposed in the cavity and operative coupled to the eccentric. An example of such an embodiment is illustrated in FIG. 1 which includes cylinder block 80, bearing assembly 82, cylindrical cavity 84 and roller piston 86.
The present invention further provides a hermetic compressor assembly including a compressor housing, a compression mechanism disposed in the housing, a motor disposed in the housing, and a crankshaft operatively coupling the compression mechanism and the motor and having an axis of rotation. The crankshaft includes an eccentric portion and means for balancing the crankshaft. The eccentric portion has a cylindrical surface and a central axis on one radial side of the axis of rotation, and further defines a circular axial profile. The means for balancing the crankshaft is integrally formed with the crankshaft opposite the eccentric portion and is contained within the circular axial profile.
The present invention further provides a crankshaft for a hermetic compressor assembly and having an axis of rotation, including a cylindrical eccentric portion and a counter eccentric lobe. The eccentric portion has a central axis, is located on one radial side of the axis of rotation, and defines a circular axial profile. The counter eccentric lobe is integrally formed with the crankshaft on the radial side of the crankshaft opposite the eccentric portion, is located axially adjacent the eccentric portion, and is located within the circular axial profile.